Oops, guess I mis-remembered Spitchwick’s details!
I don’t know that GAGB have any powers with Groundspeak themselves other than a community group that petitions and then publicises (bad news). My concern more is the influence they have over the UK Reviewers.
Unless you’re a member I doubt you can influence their actions at all, they do seem very closed ranks and quite unwilling to enter into discussions – perhaps as a result of criticism from those such as me – but my view is they take themselves far too seriously and see themselves as saviours of geocaching, without actually fighting our corner at all. (Just a personal view, which may change)
I don’t see anything stopping individuals or other groups approaching anyone in the name of geocaching to negotiate permissions and then publicising the findings. The reviewers should accept decent proof as per groundspeak’s rules, even if it doesn’t come from the GAGB (as they did with Dave’s SSSI agreement)